Normally, mail.local delivers mail to a file owned by the recipient user in a central directory. That directory is usually /var/mail or /var/spool/mail.

Beginning with V8.12 sendmail, you can tell mail.local to instead deliver mail to a file in each user's home directory. Simply use the -h command-line switch to specify a filename that will be common across all user's homes. For example:

-h mbox

Some pop3 servers move a users' central mail to that user's home mbox file before transferring it via pop to the user. At such sites, when pop3 is so configured, and when all users read their mail with popd, there is an advantage to delivering directly to each user's mbox file with mail.local.